Treatment of carbonaceous solids



5, 1952 G. D. CREELMAN 2,606,145

TREATMENT OF CARBONACEOUS SOLIDS Filed May 15, 1948 INVENTOR GEORGED.CREELMAN T y Fwy;

A TORNEY Patented Aug. 5, 1952 TREATMENT OFCARBONACEOUS? SOLIDS GeorgeD. Creelman, Cleveland Heights, Ohio,

assignor to Pittsburgh Consolidation-Coal Company, Pittsburgh, Pa., acorporation of Pennsylvania Application May 1948, Serial No. 27,234

1 Claim. 1

The. present invention relates to the treatment of. solids and, moreparticularly, to the distillation. of carbonaceous solids such ascoal,.lignite, and the like.

It has hitherto beenproposed to effect low temperature distillation ofcoal by maintaining ,a fluidized bed of finely divided coal in a-vesselat a temperature within the low temperature distillation range of thecoal being treated. The fluidization of the coal is eifected byoxygen-containing gases, or superheated steam or both. The heat requiredto elevate the bed to the desired distillation temperature is providedeither by partial oxidation of the coal products or by the sensible heatcontained in superheated steam. Partial combustion of the coal isundesirable because part of the coal is thereby rendered unavailable forthe production of the distillation products. The use of superheatedsteam is likewise undesirablebecause of the cost of heating the steam.It would be desirable if a method and apparatus could be developed foreffecting both heating and fiuidization of the coal in the distillationzone without utilizing part of the coal which is to be distilled andwithout having to use superheated steam.

The primary object'of the present invention is to provide an improvedmethod and apparatus for effecting low temperature distillation ofcarbonaceous solids.

Another object of the present invention is to effect low temperaturedistillation of coal in a fluidized bed without utilizing part of theavailable distillable coal as a source of heat.

A further object of my invention is to provide a method and apparatusfor the low temperature lation zone and are then, conveyed to acombustion zone where they are substantially completely burned. The hotcombustion gaseous products are thereafter circulated through the bed offinely divided solids in the distillation zone. The tem perature, thevolume, and the superficial velocity 1 of the volatilehot combustionproducts are regulated in such a manner as to effect fluidization of thecarbonization solids in the distillation zone and also to elevate thetemperature thereof to the desired distillation temperature. It is thusap- Other objects and advantages than those above specified will beapparent from the following.

Referring to the drawing, numeral [0- desige nates a distillation zonewhich comprisesasta tionary Vertical vessel I2 in which a fluidizedbed.M of carbonaceous solids is adapted to be main: tained. A hopper l6serves to supply finely di.-' vided carbonaceous solids through conduitl 8.t'o. a screw feeder which is drivenby motori22. The screw feedercommunicates as shownwith.

' the upperportion of the-vessel l2. Conduit .24

connects the-top of the vessel 12 witha cyclone. separator 26. Thelatter in turn is connected through a conduit 28 toa second cyclonesepae rator 30. A conduit 32 serves to convey gaseousv products from thecyclone to suitable purificartion and treatment zones while a conduit 34serves to carry away the separated solids, ash-,in, this case. A conduit36 conveys solids from the cyclone separator 26 under the control ofa:regulating valve 38 to a conduit 40 through which air is circulatedunder the control of a valve 42.: Theair and'solids are conducted to acombustion zone. 44 which as shownis a powdered fuel burner-.1

- Supplemental air may also be introduced intothe.

system bymeans of conduit 64 under the control; of valve 48. Steam maybe introduced through; conduit 50. The hot combustion productsfrom theburner-44" are carried by conduit .52 :tosthe bottom of the vessel I2..

The solid products of distillationain the vessel 12 are carried away byconduit 54 through a-cooler 56'and thereafter to a separation zone 58:-The latter is a vessel through whichair is'introduced? through conduit60. The-air and-entrainedrdust' are conducted away from the vesselthrough ;.a. conduit 62 at the top. Dust-freersolidsxare ire'e movedfrom the vesselthroughj conduit 64;

The operation of myv invention as applied .tothe' distillation of coalwill now bedescribed forthe.

purpose of illustration only and not bywayxof; limitation; ilinelydividedcoal (i; er, all ranks: of coal: including lignite) is fed:into the vessel v I2 from the hopper ls-by means of screw' f'eeder 2B.Initially, in order to establish a fiuidizedzbed of this coal in thevessel 12; it is necessary to icir' culate a fluidizinggas'therethroug-h which, inthis instance, may be air fed through conduit52;- 'By" partial combustion of the coal, the temperature within thedistillation zone is raised to a point where distillation takes place,which, for bituminous coal, is of the order of 800 F. to 1400 F. Thetemperature, however, is one which is readily determined by experiment.Distillation of coal results in the production of volatile products anda solid char-like material which is still high in carbon content. Whilethis char is substantially the same size as the finely divided coalintroduced into the distillation zone, a certain amount of extremelyfinely divided char is produced as a result of agitation in the bed,etc. These so called fines become entrained in the fiuidizing gas andvolatile products and are ordinarily carried along with such gases tosuitable purification and separation apparatus.

According to the present invention, the mixture ofv gases and entrainedfines are conducted through conduit 24 to the cyclone separator 26 wherethe fines are deposited from the gases. They are led through the conduit36 to conduit 40 wherethey are picked up and conveyed to the burner 34by air in conduit 40. The quantity of fines fed to the burner iscontrolled by regulator 38. Substantially complete combustion of thefines is effected in the burner by air introduced either as the carryingmedium for the fines through conduit 40 under the control of valve 42,or by introducing supplemental air through conduit 46 under the controlof valve 48. Steam may also be introduced into the burner throughconduit 50 in the well known manner if it is desired to eifectdistillation of the coal in the presence of steam or to supplement theheat produced by the burner 44. By regulation of the amount of fines,air and steam (if any) introduced into the burner, the total volume ofcombustion products can be regulated so as to provide a fluidizing gassuitable for effecting fluidization of the finely divided coal in thevessel l2 at the desired distillation temperature. Where the temperatureof the distillation zone is in the neighborhood of 800 F. to 1400 F., Ihave found it desirable to provide hot combustion products from theburner 44 at a temperature of 1400" F. to 1600 F.

The ash from the burner 44 is very fine fly ash which ordinarily will becarried through the distillation zone I and on through the first cycloneseparator 26. From this separator the fine fly ash is carried by thesolid products through conduit 32 to a second separator which isrequired to effect complete separation of the me fly ash from thegaseous products. The fly ash is then led away through conduit 34 whilethe volatile products are conducted through conduit 32 for furthertreatment.

The char products of distillation are removed from the vessel l2 throughconduit 54 and are conducted to a cooler 56 for reducing the temperatureto the point where it can be handled. In some instances, it may bedesired to conduct this char directly to other reaction zones fortreatment wherein the char is gasified for the production of carbonmonoxide and hydrogen mixtures and the like. From the cooler, char isconducted to a chamber 58 where air introduced through conduit 60 is ledthrough the finely divided hot char and out the top through conduit 62.This air serves to remove from the char any fine fly ash which may becarried along with the char from the vessel l2. The dust free char isthen conducted from the chamber 68 through conduit 64.

It will thus be seen from the above that a method and apparatus aredisclosed which utilizes the minimum amount of heat and extraneous gasesto effect distillation of coal and similar substances to yield liquidand gaseous products as Well as solid carbonaceous materials. The liquidproducts in the case of coal are liquid tars which may serve as fuels oras a source of chemicals. The gaseous products are high B. t. u. gasesuseful as fuels. The solid products, known as char or semi-coke may beused as fuel or as a raw material for the production of gases.

While I have described my invention as applied to the low temperaturedistillation of carbonaceous solids, it will be readily apparent that itis generally applicable to the treatment of carbonaceous solids whereverheat is required to effect the treatment and wherever an appreciableamount of carbonaceous fines are carried away from the treatment zone byproduct gases, etc.

According to the provisions of the patent statutes, I have explained theprinciple, preferred construction, and mode of operation of my inventionand have illustrated and described What I now consider to represent itsbest embodiment. However, I desire to have it understood that, withinthe scope of the appended claim, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

The method of treating carbonaceous solids which comprises circulatinggas through a bed of finely divided carbonaceous solids at an elevatedtemperature under fluidizing conditions in a confined reaction zone,feeding fresh carbonaceous solids to said reaction Zone to maintain thedesired level of said fluidized bed, conducting eiiluent gases andcarbonaceous solid fines which are entrained in said efiluent gases fromsaid reaction zone to a separation zone separating said fines from saideiiluent gases in said separation zone, separately withdrawing solidswhich are not entrained in the effluent gases from the fluidized bed,effecting substantially complete combustion of said separatedcarbonaceous fines and only said fines in a combustion zone which isseparate from said reaction zone, thereafter recirculating the hot gasesand fine ash from said combustion zone through said fluidized bed indirect heat exchange relation therewith, and separating said efiiuentgases from said fine ash after circulation through said separation zonewhere said carbonaceous fines are removed.

GEORGE D. CREELMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

